/*
 * Copyright 2002-2019 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package cn.cloud.all.security.oauth2.client;

import cn.cloud.all.security.core.AbstractOAuth2Token;
import cn.cloud.all.security.oauth2.endpoint.OAuth2RefreshTokenGrantRequest;
import cn.cloud.all.security.oauth2.endpoint.ReactiveOAuth2AccessTokenResponseClient;
import cn.cloud.all.security.oauth2.endpoint.WebClientReactiveRefreshTokenTokenResponseClient;
import org.springframework.util.Assert;
import reactor.core.publisher.Mono;

import java.time.Clock;
import java.time.Duration;
import java.time.Instant;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;

/**
 * An implementation of a {@link ReactiveOAuth2AuthorizedClientProvider}
 * for the {@link AuthorizationGrantType#REFRESH_TOKEN refresh_token} grant.
 *
 * @author Joe Grandja
 * @see ReactiveOAuth2AuthorizedClientProvider
 * @see WebClientReactiveRefreshTokenTokenResponseClient
 * @since 5.2
 */
public final class RefreshTokenReactiveOAuth2AuthorizedClientProvider implements ReactiveOAuth2AuthorizedClientProvider {
    private ReactiveOAuth2AccessTokenResponseClient<OAuth2RefreshTokenGrantRequest> accessTokenResponseClient = new WebClientReactiveRefreshTokenTokenResponseClient();
    private Duration clockSkew = Duration.ofSeconds(60);
    private Clock clock = Clock.systemUTC();

    /**
     * Attempt to re-authorize the {@link OAuth2AuthorizationContext#getClientRegistration() client} in the provided {@code context}.
     * Returns an empty {@code Mono} if re-authorization is not supported,
     * e.g. the client is not authorized OR the {@link OAuth2AuthorizedClient#getRefreshToken() refresh token}
     * is not available for the authorized client OR the {@link OAuth2AuthorizedClient#getAccessToken() access token} is not expired.
     *
     * <p>
     * The following {@link OAuth2AuthorizationContext#getAttributes() context attributes} are supported:
     * <ol>
     *  <li>{@code "org.springframework.security.oauth2.client.REQUEST_SCOPE"} (optional) - a {@code String[]} of scope(s)
     *  	to be requested by the {@link OAuth2AuthorizationContext#getClientRegistration() client}</li>
     * </ol>
     *
     * @param context the context that holds authorization-specific state for the client
     * @return the {@link OAuth2AuthorizedClient} or an empty {@code Mono} if re-authorization is not supported
     */
    @Override
    public Mono<OAuth2AuthorizedClient> authorize(OAuth2AuthorizationContext context) {
        Assert.notNull(context, "context cannot be null");

        OAuth2AuthorizedClient authorizedClient = context.getAuthorizedClient();
        if (authorizedClient == null || authorizedClient.getRefreshToken() == null || !hasTokenExpired(authorizedClient.getAccessToken())) {
            return Mono.empty();
        }

        Object requestScope = context.getAttribute(OAuth2AuthorizationContext.REQUEST_SCOPE_ATTRIBUTE_NAME);
        Set<String> scopes = Collections.emptySet();
        if (requestScope != null) {
            Assert.isInstanceOf(String[].class, requestScope,
                    "The context attribute must be of type String[] '" + OAuth2AuthorizationContext.REQUEST_SCOPE_ATTRIBUTE_NAME + "'");
            scopes = new HashSet<>(Arrays.asList((String[]) requestScope));
        }
        ClientRegistration clientRegistration = context.getClientRegistration();

        OAuth2RefreshTokenGrantRequest refreshTokenGrantRequest = new OAuth2RefreshTokenGrantRequest(clientRegistration, authorizedClient.getAccessToken(), authorizedClient.getRefreshToken(), scopes);

        return Mono.just(refreshTokenGrantRequest)
                .flatMap(this.accessTokenResponseClient::getTokenResponse)
                .map(tokenResponse -> new OAuth2AuthorizedClient(clientRegistration, context.getPrincipal().getName(),
                        tokenResponse.getAccessToken(), tokenResponse.getRefreshToken()));
    }

    private boolean hasTokenExpired(AbstractOAuth2Token token) {
        return this.clock.instant().isAfter(token.getExpiresAt().minus(this.clockSkew));
    }

    /**
     * Sets the client used when requesting an access token credential at the Token Endpoint for the {@code refresh_token} grant.
     *
     * @param accessTokenResponseClient the client used when requesting an access token credential at the Token Endpoint for the {@code refresh_token} grant
     */
    public void setAccessTokenResponseClient(ReactiveOAuth2AccessTokenResponseClient<OAuth2RefreshTokenGrantRequest> accessTokenResponseClient) {
        Assert.notNull(accessTokenResponseClient, "accessTokenResponseClient cannot be null");
        this.accessTokenResponseClient = accessTokenResponseClient;
    }

    /**
     * Sets the maximum acceptable clock skew, which is used when checking the
     * {@link OAuth2AuthorizedClient#getAccessToken() access token} expiry. The default is 60 seconds.
     * An access token is considered expired if it's before {@code Instant.now(this.clock) - clockSkew}.
     *
     * @param clockSkew the maximum acceptable clock skew
     */
    public void setClockSkew(Duration clockSkew) {
        Assert.notNull(clockSkew, "clockSkew cannot be null");
        Assert.isTrue(clockSkew.getSeconds() >= 0, "clockSkew must be >= 0");
        this.clockSkew = clockSkew;
    }

    /**
     * Sets the {@link Clock} used in {@link Instant#now(Clock)} when checking the access token expiry.
     *
     * @param clock the clock
     */
    public void setClock(Clock clock) {
        Assert.notNull(clock, "clock cannot be null");
        this.clock = clock;
    }
}
